On The Thousand-Year Elven Holocaust.
In their books, both Nicholas de Vere and Laurence Gardner refer to the "Thousand Year Elven Holocaust," in which they claim the Romans, and later the Roman Catholic Church, oppressed the Elven peoples. It's important to remember at this point that both authors claim that the myths and legends of the "Elven" peoples were inspired by the Royal Scythian tribe that dwelled in the Black Sea Area and Asia Minor (the area around modern-day Romania, Ukraine, Turkey, and Iraq) and that the bloodlines of the "Grail" dynasties sprung from them via intermarriages between this tribe and Egyptian and Hebrew royalty in ancient times. The "Elves" spoken of by both authors in this case are said to be their descendants.
The 2003 release of Dan Brown's The Da Vinci Code sent the Catholic Church into a tizzy, because of claims that Yeshua ben Joseph (known nowadays as Jesus Christ) married Mary Magdalene and had children, siring the line of the Merovingian kings. Jesus was said to be of the house of David, and any descendants of His (if He had them) would have been of the Davidic (Desposynic) descent.
This is apparently an idea that has come and gone throughout the last two millennium, but which first sprang back into public consciousness when Pierre Plantard perpetuated his famous Priory of Sion hoax. Authors Michael Baigent, Henry Lincoln, and Richard Leigh ran with this idea in their book Holy Blood, Holy Grail, which helped to popularize the idea that Dan Brown would later work into The Da Vinci Code. The idea was that the Merovingians had once ruled as the true kings of France and a huge chunk of ancient Europe besides via a divine mandate, and that the Pope had upset the natural order of things by deposing them with the Donation of Constantine.
Is it truth? Did Jesus marry, and found a bloodline of ancient kings? Whatever else you believe about the Merovingians, we are now coming to the part that can actually be historically verified without a doubt; there is no argument that the Roman Catholic Church systematically persecuted and disenfranchised every group that is said to be associated with the Grail Bloodlines by the aforementioned authors. The Merovingians, the Cathars, and the Knights Templar all suffered at the hands of the Roman Pontiffs, who slandered them, tortured them, slaughtered them, and seized their lands in a series of coups, crusades, and inquisitions during the middle ages, such as the Albigensian Crusade from 1209-1229 AD, and the campaign of persecution that took place against the Templars in 1307 AD.
The reason given for the Church's campaign against the Cathars is generally that they were practitioners of a form of Gnostic Christianity, which the Roman Church considered to be heretical. Though the Templars were supposed to have been the militaristic arm of the Church before their fall from Papal grace, there are signs that they may have been influenced by their proximity to the Cathars, and many have theorized that the Templars who managed to escape to Scotland would go on to form the Freemasons. But the Church's treatment of the Templars is probably more related to the fact that the Pope Clement V and the French King Philip IV coveted ownership of the Templar Order's lands and money. The "Templar Conspiracy" may not be any more mysterious or complicated than that.
EDIT: 10/17/09: This section of the website about the Pickingill Papers documents the Roman Church's campaign of persecution against pretty much anyone who disagreed with them during the Middle Ages. All of the groups I have listed in this article are mentioned, though the article on that site focuses mainly upon the plight of followers of the Old Religion who were maligned by the Church.What to do about this now? Well, Pope John Paul II apologized for the Crusades and the Inquisitions, and the Catholic Church is now just one of many denominations within the Christian faith. With all of the hullabaloo about the supposed marriage of Jesus to Mary Magdalene, one wonders why they weren't up in arms about the other side of the tale: the public reminder that at one time they had participated in a genocidal pogrom on the level of Adolph Hitler or Joseph Stalin. But as this aspect of the story was glossed over by The Da Vinci code, it didn't seem to gain as much attention. The point is to remember that it happened, so that these peoples and the persecution they suffered are not forgotten.